The present invention relates to the art of electroplating and particularly to the art of electroplating small articles, for example portions of the interior of small tubular metallic parts where the electroplated portions are used in the electronics industry as contact surfaces and relates more particularly to the art of goldplating the inner surface of tubular electronic components.
The growth and increased sophistication of the electronics industry has led to the need for electroplated components and particularly for electoplated contact areas of various description where the contact areas are usually electroplated with gold which has been found to be particularly effective to prevent corrosion and erosion of contact areas and maintain reliable electrical conductivity of the components.
Gold has become recognized as the leading plating material because of its relative unalterability, good solderability and low contact resistance.
The prior art teaches one method for plating of such contacts which has become known as "barrel plating" where the articles are tumbled in a barrel of plating liquid for application of the plating.
The barrel plating method is expensive because of the increased price of gold coupled with the use of excess material required in such procedures because of the waste of plating fluid and because such techniques are not specific as to areas to be electroplated and lead to plating unnecessary areas and overplating. Accordingly, the use of techniques to plate only contact surfaces as provided by the present invention have come to be appreciated.
One prior art arrangement for selective plating is shown in U.S. Pat. No. 3,904,489 which utilizes a porous felt type applicator which is used to apply the electroplating solution to the parts which are carried by a continuous belt by insertion therethrough. However, this technique is generally ineffective to accomplish plating of the inner surface of a tubular post.
Another prior art arrangement which is an improvement in the aforenoted arrangement is shown in U.S. Pat. No. 3,966,581.
Another arrangement is shown in my U.S. Pat. No. 4,404,078 to apparatus which can be utilized in the electroplating of elongate parts including tubular parts but are not limited thereto.
U.S. Pat. No. 3,878,062 teaches a method for selective plating through the use of direct impingement of the electroplating solution and U.S. Pat. No. 3,657,097 teaches the use of solution height adjustment for selective plating. Also U.S. Pat. No. 4,032,414 teaches carriages to transfer two pin strips through electroplating solutions and U.S. Pat. No. 4,035,245 teaches control of electroplating systems through fluid control vanes which regulate flow of the electroplating fluid to effect selectivity.
One prior art method shown in German Pat. No. 2,019,178 teaches agitation of the electroplating bath to plate non moving parts in an electroplating bath but none of the known prior art references teaches vibration of the bath at ultrasonic frequency to effect the plating of the inside of tubular articles.
Further, no prior art device is known to accomplish continuous electroplating of the inside of a portion of tubular articles where the articles are carried in selected orientation in a receiver which covers the outside of the part which is conveyed through an electroplating bath by a moving conveyor where the parts are dipped in the bath to electroplate only inside portions thereof while electrical contact is maintained from a contact strip in contact with the article while the downwardly depending portion of the article to be electroplated is immersed in the electroplating solution and the solution is vibrated at ultrasonic frequency.